Makers of applications that locate drunk-driving checkpoints are misunderstood, defenders said Wednesday, a day after four U.S. senators called for smartphone makers to pull applications from their services.

The applications do more than identify drunk-driving checkpoints set up by police, and the DUI (driving under the influence) checkpoint functionality actually aids police, said Joe Scott, CEO and founder of PhantomALERT, one of the companies targeted by the senators.

"They're misjudging us," Scott said Wednesday. "It's a safety tool. It's approved by a lot of police departments. How is that we're being sanctioned? It just doesn't make sense."

When users of PhantomALERT report DUI checkpoints, it often appears to users that there are more checkpoints than actually exist, Scott said. The result is the app "deters people from drinking and driving," he added. "We're like a force multiplier for them."

The Association for Competitive Technology (ACT), a Washington, D.C., trade group, also questioned the request from Senators Harry Reid of Nevada, Charles Schumer of New York, Frank Lautenberg of New Jersey and Tom Udall of New Mexico. The four Democrats sent a letter to smartphone software vendors Apple, Google and Research In Motion Tuesday, asking them to stop selling DUI checkpoint apps.

The letter didn't name the DUI checkpoint software, but PhantomALERT was one of several companies targeted, a Senate spokeswoman said. Similar software includes Cobra's iRadar, Trapster and Fuzz Alert.

On Wednesday, the senators reported that RIM would remove the DUI checkpoint apps. "Drunk drivers will soon have one less tool to evade law enforcement and endanger our friends and families," the senators said in a statement. "We appreciate RIM's immediate reply and urge the other smartphone makers to quickly follow suit."

But the apps in question contain publicly available information provided by police departments as well as reports from drivers, said Morgan Reed, ACT's executive director. The social-networking and law enforcement information makes the apps very popular, he said.

"While I applaud the senators for seeking to curb drunk driving, their criticism of online travel apps misses the point," he said. "Law enforcement authorities have embraced these services, expressing their strong approval for products that reduce speeding and improve traffic safety."

The apps provide drivers warnings about other potential roadway problems, Reed said. "Any one of the programs' users can submit a warning about a traffic obstruction as simply as e-mailing a friend or posting a message on their Facebook profile," he added. "The suggestion that the government should compel Apple, RIM, or other mobile application stores to block programs that simply allow users to report information based on location is misguided at best. Having the government act as arbiter of which products should be sold in stores is a slippery slope that few would welcome."

Asked if the senators' letter amounted to the government compelling action of the smartphone makers, ACT spokesman Jonathan Godfrey suggested it did. "When the Senate majority leader [Reid] and his senate colleagues send a letter urging you to do something, implicit is that they can have hearings and examine legislative fixes if you don't address their concerns," he said.

When police departments set up DUI checkpoints, they often advertise their plans, added Scott. "All we're doing is we're taking information and pushing it toward the drivers," he said. "A lot of police departments are saying that part of the campaign is awareness. If PhantomALERT gets the word out ... that's going to deter a lot of people from drinking and driving."